Some electronic systems require the use of variable or tunable capacitors that can operate under high power conditions. Exemplary of such applications are magnetic imaging equipment and particle accelerators. Heretofore, such high power, tunable capacitors have predominantly been constructed with two sets of a number of concentric metallic cylinders nested in an air dielectric with capacitance being varied by axial displacement of one set of the cylinders with respect to the other. Exemplary of such is the capacitor shown in U.S. Pat. No. 4,459,635. With their large number of cylinders electrically connected in parallel, they inherently have had to be physically large. This consumption of space often presents serious problems to system designers. This has also rendered them heavy which has, in turn, tended to cause them to vibrate in many environments. Furthermore, their large dimensions have increased their electrical inductance.
In addition to the foregoing, the need for a large number of stator and rotor cylinders or plates, 40 being representative, has rendered high power, tunable capacitors of the prior art quite costly to manufacture. Having a large number of parts that must be assembled with precision has also rendered them unreliable. They usually have had to have one terminal movable with respect to another which has further complicated their incorporation into circuits. Their temperature coefficients have also been fixed by the use of air as their dielectric medium.
It thus is seen that a need has long existed for a high power, tunable capacitor of simpler, more economic and reliable construction. It is to the provision of such that the present invention is primarily directed.